fix: adjust EIP-7742 to latest spec (#1713)

Author: klkvr

crates/consensus/src/block/header.rs

@@ -221,18 +221,9 @@ impl Header {
     ///
     /// Returns `None` if `excess_blob_gas` is None.
     ///
-    /// If [`Self::target_blobs_per_block`] is [`Some`], uses EIP-7742 formula for calculating
-    /// the blob gas price, otherwise uses EIP-4844 formula.
-    ///
     /// See also [Self::next_block_excess_blob_gas]
     pub fn next_block_blob_fee(&self) -> Option<u128> {
-        let next_block_excess_blob_gas = self.next_block_excess_blob_gas()?;
-
-        if self.target_blobs_per_block().is_none() {
-            Some(eip4844::calc_blob_gasprice(next_block_excess_blob_gas))
-        } else {
-            Some(eip7742::calc_blob_gasprice(next_block_excess_blob_gas))
-        }
+        Some(eip4844::calc_blob_gasprice(self.next_block_excess_blob_gas()?))
     }
 
     /// Calculate base fee for next block according to the EIP-1559 spec.
@@ -253,9 +244,6 @@ impl Header {
     /// If [`Self::target_blobs_per_block`] is [`Some`], uses EIP-7742 formula for calculating
     /// the excess blob gas, otherwise uses EIP-4844 formula.
     ///
-    /// Note: this function will return incorrect (unnormalized, lower) value at EIP-7742 activation
-    /// block. If this is undesired, consider using [`eip7742::calc_excess_blob_gas_at_transition`].
-    ///
     /// Returns a `None` if no excess blob gas is set, no EIP-4844 support
     pub fn next_block_excess_blob_gas(&self) -> Option<u64> {
         let excess_blob_gas = self.excess_blob_gas?;
@@ -691,9 +679,6 @@ pub trait BlockHeader {
     /// If [`BlockHeader::target_blobs_per_block`] is [`Some`], uses EIP-7742 formula for
     /// calculating the excess blob gas, otherwise uses EIP-4844 formula.
     ///
-    /// Note: this function will return incorrect (unnormalized, lower) value at EIP-7742 activation
-    /// block. If this is undesired, consider using [`eip7742::calc_excess_blob_gas_at_transition`].
-    ///
     /// Returns a `None` if no excess blob gas is set, no EIP-4844 support
     fn next_block_excess_blob_gas(&self) -> Option<u64> {
         let excess_blob_gas = self.excess_blob_gas()?;
@@ -715,18 +700,9 @@ pub trait BlockHeader {
     ///
     /// Returns `None` if `excess_blob_gas` is None.
     ///
-    /// If this header has `target_blobs_per_block` set, uses EIP-7742 formula for calculating
-    /// the blob gas price, otherwise uses EIP-4844 formula.
-    ///
     /// See also [BlockHeader::next_block_excess_blob_gas]
     fn next_block_blob_fee(&self) -> Option<u128> {
-        let next_block_excess_blob_gas = self.next_block_excess_blob_gas()?;
-
-        if self.target_blobs_per_block().is_none() {
-            Some(eip4844::calc_blob_gasprice(next_block_excess_blob_gas))
-        } else {
-            Some(eip7742::calc_blob_gasprice(next_block_excess_blob_gas))
-        }
+        Some(eip4844::calc_blob_gasprice(self.next_block_excess_blob_gas()?))
     }
 
     /// Calculate base fee for next block according to the EIP-1559 spec.

crates/eips/src/eip7742.rs

@@ -1,64 +1,18 @@
 //! Contains constants and utility functions for [EIP-7742](https://eips.ethereum.org/EIPS/eip-7742)
 
-use crate::eip4844::{self, fake_exponential, BLOB_TX_MIN_BLOB_GASPRICE, DATA_GAS_PER_BLOB};
-
-/// Controls the update rate of the blob base fee based on `target_blobs_per_block`.
-pub const BLOB_BASE_FEE_UPDATE_FRACTION_PER_TARGET_BLOB: u128 = 1112825;
-
-/// Controls the update rate of the blob base fee based on `target_blobs_per_block`.
-pub const EXCESS_BLOB_GAS_NORMALIZATION_TARGET: u64 = 128;
-
-/// Same as [`eip4844::BLOB_GASPRICE_UPDATE_FRACTION`], but normalized for the target of 128
-/// blobs.
-pub const BLOB_BASE_FEE_UPDATE_FRACTION_NORMALIZED: u128 =
-    BLOB_BASE_FEE_UPDATE_FRACTION_PER_TARGET_BLOB * EXCESS_BLOB_GAS_NORMALIZATION_TARGET as u128;
-
-/// Calculates the `excess_blob_gas` for the header of the block enabling EIP-7742.
-///
-/// Normalizes the parent's excess blob gas as per EIP-7742.
-#[inline]
-pub const fn calc_excess_blob_gas_at_transition(
-    parent_excess_blob_gas: u64,
-    parent_blob_gas_used: u64,
-) -> u64 {
-    let normalized_parent_excess_blob_gas = parent_excess_blob_gas
-        * EXCESS_BLOB_GAS_NORMALIZATION_TARGET
-        / eip4844::TARGET_BLOBS_PER_BLOCK;
-
-    calc_excess_blob_gas(
-        normalized_parent_excess_blob_gas,
-        parent_blob_gas_used,
-        eip4844::TARGET_BLOBS_PER_BLOCK,
-    )
-}
+use crate::eip4844;
 
 /// Calculates the `excess_blob_gas` from the parent header's `blob_gas_used`, `excess_blob_gas` and
 /// `target_blobs_per_block`.
 ///
-/// Note: this function assumes that the parent block's excess blob gas is normalized as per
-/// EIP-7742.
+/// Similar to [`eip4844::calc_excess_blob_gas`], but uses the `target_blobs_per_block` to calculate
+/// the target gas usage.
 #[inline]
 pub const fn calc_excess_blob_gas(
     parent_excess_blob_gas: u64,
     parent_blob_gas_used: u64,
     parent_target_blobs_per_block: u64,
 ) -> u64 {
-    let normalized_blob_gas_used =
-        parent_blob_gas_used * EXCESS_BLOB_GAS_NORMALIZATION_TARGET / parent_target_blobs_per_block;
-    let normalized_target_blob_gas = DATA_GAS_PER_BLOB * EXCESS_BLOB_GAS_NORMALIZATION_TARGET;
-
-    (parent_excess_blob_gas + normalized_blob_gas_used).saturating_sub(normalized_target_blob_gas)
-}
-
-/// Calculates the blob gas price from the header's excess blob gas field.
-///
-/// Similar to [crate::eip4844::calc_blob_gasprice], but adjusts the update rate based on
-/// `target_blobs_per_block`.
-#[inline]
-pub fn calc_blob_gasprice(excess_blob_gas: u64) -> u128 {
-    fake_exponential(
-        BLOB_TX_MIN_BLOB_GASPRICE,
-        excess_blob_gas as u128,
-        BLOB_BASE_FEE_UPDATE_FRACTION_NORMALIZED,
-    )
+    (parent_excess_blob_gas + parent_blob_gas_used)
+        .saturating_sub(parent_target_blobs_per_block * eip4844::DATA_GAS_PER_BLOB)
 }